On-site facilities such as power plants and plants are provided with a large number of measuring instruments (for example, needle-type meters) that measure physical quantities such as the amount of water flowing through a pipe. These measuring instruments have been used for facility inspections performed by human visual observation in a cycle of about several times a day or more frequently. In maintenance and inspection work, however, problems have arisen such as aging of inspection workers and securing of personnel.
From this viewpoint, a system, which images a display unit of a measuring instrument with a camera and transmits such captured image data via a wireless network, is developed to obtain automation of inspection work (see, for example, PTL 1). PTL 1 states that “it relates to a meter reading method by image processing suitable for accurately reading positions of pointers of meters in the image processing using a monitor television camera”.
Further, there is a technique of suppressing an increase in communication time in a wireless meter reading system using a wireless communication network by performing retry (re-transmission) of communication in a wireless master station when communication between a portable master device and a wireless slave station (wireless slave device) fails (see, for example, PTL 2). PTL 2 states that “the portable master device transmits a batch meter reading request telegram to the wireless slave stations, and receives response telegrams for the batch meter reading request telegram from the respective wireless slave stations. The portable master device determines and classifies each failure cause when the communication fails for each of the wireless slave stations from which the response telegram has not been received, and performs retry (re-transmission) by batch communication for each classification”.